On Fri, Apr 4, 2014 at 11:15 AM, Merlin Moncure <mmoncure@gmail.com> wrote:
> On Fri, Apr 4, 2014 at 11:04 AM, Steve Crawford
> <scrawford@pinpointresearch.com> wrote:
>> On 04/03/2014 12:44 PM, Brent Wood wrote:
>> 2. Do I need both BBU on the RAID *and* capacitor on the SSD or just on one?
>> Which one? I'm suspecting capacitor on the SSD and write-through on the
>> RAID.
>
> You need both. The capacitor protects the drive, the BBU protects the
> raid controller.
You don't technically need the BBU / flashback memory IF the
controller is in write through. My experience has been that the BBU
helps a lot on write heavy applications or to get maximum performance
for your money. On most cards, it's < $100 so unless you can
definitively show no real performance loss without one, get one. OTOH
it's worth testing to be sure. But the BBU does a lot to reorder
writes and such and flattens out bursty write performance very well.
It also speeds up checkpointing if / when it has to occur.
